Broad band antenna



Sept. 27, 1949. w. w. HANSEN BROAD BAND ANTENNA Filed Sept. 6, 1945ATTORN EY Patented Sept. 27, 1949 BROAD BAND ANTENNA William W..Hansen,Garden City, N. Y. assignor to The Sperry Corporation, a corporation :of

Delaware Application September 6, 1943, Serial No. 501,370

12 Claims. (C1. 250-3351) My invention relates to antennae or radiatorsfor radio communication and signaling systems, and concerns particularlyradiators suitable for use in high frequency radio systems such as maybe used in connection with object detection.

An object of my invention-is toprovide an antenna having a pattern likean end-fire array of dipoles, but having a broader frequency band.

A further object of my invention is to provide a balanceddouble-endedantenna which is useful in pulse systems and in whichsparking is prevented.

A further object of my invention is to provide an antennagivingcircularzpolarization of radiation-and reception.

Other and further objects and advantages will become apparent as the*descriptionproceeds.

In carrying'out my'invention in its preferred form, I utilize a-rod orwire of-suitableconducting material which is electrically continuousfrom one input'terminal tothe other, which is bent into helical formandhas a diameter and pitch of the helix of such a value in relation tothe desired wave-length that radiation from all elements of the antennais in phase.

A better understanding of the invention will be afiorded by thefollowing detailed description considered in connection with theaccompanying drawing, in which Fig. 1 is a diagram representing afragmentary end view of one embodiment of my invention, and

Fig. 2 is a perspective diagram of the embodiment of my inventionrepresented in Fig. 1.

Like reference characters are utilizedthroughout the drawing todesignate like parts.

The antenna illustrated in the drawing comprises a unitary length ofwire H which is bent in the form of a helix. In order that running wavesinstead of a standing wave may be produced, and in order that a suitabletermination may be conveniently connected to the antenna I prefer toprovide a pair of helices l2 and i 3 each formed of a length of wirerepresented by the separate symbols H and H.

For supplying input energy to the antenna at input terminals I4 and I5,a suitable transmission line, such as concentric line [6, may beprovided comprising an inner rod conductor I! connected to the antennaterminal I 4 and an outer cylindrical conductor I 8 connected totheantenna terminal I 5.

The helices l2 and I3 may have end terminals 2| and 22, respectively,between which a suitable terminating impedance 23 is'connected.Preferably the impedance 23 comprises a'highfrequency propagation.

resistor having a resistance such as to suppress any reflected currentwaves. In other words, the unit'2-3 has an impedance matched-to-theantenna or equalling'the characteristic impedance thereof.

.Although the value of this resistanceimay be determined bycalculation,Iconsider it preferable to determine the best valueof terminatingimpedance by trial and error.

Theform. of: antenna. illustratedis. advantageous when double-endedinputisrequiredand is .useful for producing circular polarization. Thedirection of propagation of the radiated energy is along the arrow 24.In order .that the phase relationship between the radiation andsuccessive ele- -ments will be in the samephase, the dimensions of theantenna should be so chosen that variation in phase due to the lead orpitch of the helix compensates for the Variation :in phase due to thedifference in position of said elements along the wire in any turn orportion of a turnof the wire forming the antenna. Thus, the effectofchange in direction of the wire caused 'by bending it around an axisis-overcomaby also warping it toa pitch 'or :advance along the directionsof wave It Will be understood that an antenna of this type isparticularly useful for 'high frequency radiation or radiation atfrequencies such that the wavelength :is comparable with the physicaldimensions of the antenna. Consequently, -the length of the wireis ofthe order of magnitude of a number of wavelengths, and the currents inthe successive portions of the Wire produce "radiation at successivelylater periods of time. Consequently therradiationfrom successiveelements .of the wire'would tend to vary progressively in phaserelationship if "the turns of wire -all lay in-the same plane.

Since'the'direction of propagation is along a line parallel to the helixaxes; the change in phase due to progress of the phase along the wire inany one'turn'is'compensatedby the pitch'ofthe Wire causing successiveportions "of the wire-to have different positions with respect'to thedirection'of propagation. The radiation pattern resembles that of-"an-'en'd--f1re array of dipoles.

The preferred-dimensions of'the antenna are therefore determined fromthe phase relationships of the radiation from various elements of theantenna. It may'hexshnwn that the phase of the radiation from anyelement is expressed by the equation p the phase depending on theadvance of the helix. The phase of waves running down the wires dependson km for the distance along the wire and on kP/21r for the advance ofthe helix. When 0=1r, the direction or the wire has reversed. Ihe waveswill add in front if In order to make the radiation from all elements ofthe same phase, dimensions should be chosen to satisfy the equation B r27r 21r where x is the electrical wavelength of the desired radiation.Suitable dimensions, for example, are

for the pitch P and the radius A in r 81r 811' It will be apparent thatthe required phase relationships may be obtained by using a singlehelix, such as the helix IE or l3 provided, however that the waves onthe wire are running waves. To insure this, some form of termination isneeded and the simplest way of providing for making connections to atermination is to employ a plurality of helices, in an even number, suchas 2 or a multiple thereof.

Since rotational symmetr exists with respect to the helix axes parallelto the direction of propagation 24, the radiated wave is circularlypolarized.

In accordance with the provisions of the patent statutes I havedescribed the principle of operation of my invention, together with theappara tus which I now believe to represent the best embodiment thereof,but I desire to have it understood that the apparatus shown anddescribed is only illustrative and that my invention may be carried outby other arrangements.

What is claimed is:

1. An antenna composed of a length of conductor material curved to formsuccessive elements with progressively different directions and. indifierent planes with successive elements bent along a circle with aradius r and successive elements also warped into difierent planes witha pitch P satisfying the equation where x is the electrical wave lengthof oscillations to be transmitted or received by the antenna.

2. An antenna comprising a length of conductor material bent to a radiusequal to and warped to give a pitch or advance equal to where x is theelectrical wave length of oscillations to be transmitted or received bythe antenna.

3. An antenna comprising a length of wire in the :form of a helix havinga radius T and having a helix pitch P satisfying the equation P 21r 2 1r where x is the electrical wavelength of oscillations to be transmittedor received by the antenna.

4. An antenna comprising a length of conductor material bent into theform of a helix having a radius equal to and a helix advance or pitchequal to where A is the electrical wavelength of oscillations to betransmitted or received by the antenna.

5. An antenna system for use with ultra short waves, comprising a lengthof conductor in the form of a helix having a diameterof the same orderof magnitude as the length of said waves, and means supplying radiofrequency energy to said helix, said helix having a pitch in relation tothe diameter of said helix as to cause the same variation in phase dueto the pitch of said helix as is due to the length of the conductor,whereby a unidirectional radiation pattern having a maximum directivityin the axis of the helix is formed.

6. An antenna system for producing circularly polarized ultra shortwaves, comprising a pair of conductors bent in the form of a pair ofhelices each helix having an input terminal and an end terminalconnected to the other end terminal .of said other helix of said pair ofhelices by a terminating matched impedance placed therebetween, and eachof said helices further comprising a plurality of successive loopshaving diami eters of the same order of magnitude as the length of said.waves at the operating frequency, said loops of said helices beingspaced from each other by a distance sufficient for radiation from eachof said loops to arrive in phase at the next successive loop, whereby aradiation pattern having a maximum directivity along the axes of thehelices is formed.

7. An antenna system for use with ultra short waves, comprising an evennumber .of helices connected in series, a pair of input terminals eachconnected at one end of one of the helices, a

terminating impedance connected in series with said helices and beingmatched thereto, and each of said helices further comprising a pluralityof successive loops having diameters of the same order of magnitude asthe length of said Waves at the operating frequency, said loops of saidhelices being spaced from each other by a distance suiiicient forradiation from each of said loops to arrive in phase at the nextsuccessive loop, whereby a unidirectional radiation pattern having amaximum directivity along the axes of the helices is formed.

8. An ultra high frequency antenna system for use with ultra short wavescomprising a plurality of radiating loops, means connecting each of saidloops in electrical series with respect to one another, each of saidloops being pitched from each other at a distance of the same order ofmagnitude as the length .of said waves and having a suitable diameter sothat the difference between the electrical phase displacement due to thelength of conductor and the space phase displacement due to pitch issubstantially a half-wavelength whereby radiation from each of saidloops arrives in phase reinforcement at the next successive loop to forma radiation pattern having a maximum directivity in a planeperpendicular to the plane of said loops.

9. An antenna system for use with ultra short waves comprising aplurality of parallel displaced helices connected in series, each ofsaid helices having a plurality of loops pitched in the same directionfrom each other by a distance in the same order of magnitude as saidwaves, a plurality of input terminals connected at one end .of saidhelices and a terminating matched impedance connected in series witheach of said helices so as to define a maximum radiation directivitycharacteristic for said waves along the axes of said helices.

10. In an antenna system for use with ultra short waves means forproducing circular polarization comprising a pair of parallel displacedhelices connected in series, each of said helices having a plurality ofloops pitched in the same direction from each other by a distance in thesame order of magnitude as said waves, a pair of input terminalsconnected at one end of said helices and a matched terminating impedanceconnected in series between said helices so as to define a maximumradiation characteristic for said waves along the axes of said helices.

11. A circularly polarized antenna system for use with ultra short wavescomprising a pair of conductors having the shape of parallel displacedhelices connected in series, each of said helices having a plurality ofloops pitched in the same direction from each other by a distance in thesame order of magnitude as said waves, and a terminating matchedimpedance connected between said conductors so as to define a maximumradiation directivity characteristic for said waves along the axis ofsaid helices.

12. An ultra high frequency antenna system for use with ultra shortwaves comprising a pair of adjacent helices each having a plurality ofradiating loops, said loops being connected in electrical series withrespect to one another, each of said loops having a diameter .of thesame order of magnitude as the length of said waves, a terminatingimpedance interconnecting said adjacent helices for cancelling standingwaves in said loops, said loops further being pitched from each other bya distance such that radiation from each of said loops will arrive inphase reinforcement at the next successive loop so as to form aradiation pattern of circular polarization having a maximum directivityparallel to the axes of said helices.

WILLIAM W. HANSEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain Oct.30, 1923 Number Number

